The present invention relates to a knee brace with sagittal adjustment, that is a brace or an orthotic device capable of correcting the knee joint into varus or valgus for osteoarthritis treatment. The knee brace of the invention features a special hinge portion providing a correction force to the thigh cuff and shin cuff attached to the leg of a patient in order to correct the position of the patient""s knee joint, especially during extension of the leg.
The knee joins the femur to the tibia and is controlled by ligaments and cartilage. Contact between the femur and the tibia occurs across the cartilage and there are so called compartments or spaces at each side of the knee. The medial compartment is on the inside of the knee, the lateral compartment is on the outside of the knee.
A healthy knee joint has an even distribution of pressure medially and laterially.
Unicompartmental osteoarthritis, which may occur in the medial compartment or in the lateral compartment, will result in a mechanical malfunction of the knee whereby uneven distribution of pressure occurs across the knee causing excessive wear on the inside of the knee joint in medial compartment osteoarthritis and on the outside of the knee joint in laterial osteoarthritis.
Unicompartmental osteoarthritis can be induced by injury or by aging. With the advancement of the disease, the space between the femur and tibia decreases. The problem may progress to the extent that the space is eliminated and the femur contacts the tibia. In those circumstances, erosion of the tibia may result.
With the disease there is a change in the normal angle between the femur and tibia. Lateral thrust upon heel strike often accompanies the increase in the misalignment of the femur and the tibia. This tends to stretch the ligaments on the opposite side as well as having an adverse effect on the knee joint, tending to emphasize the erosion of the tibia.
A further complication is that rotational slackness develops as the space between the compartment is reduced. This is caused by slackening of the ligaments as the attachment points of the ligaments move closer together with bone deterioration.
Various orthotic devices for knee joints are known. One type of knee brace includes double-sided positive hinge connections, that is lateral and medial hinge mechanisms, to provide a more or less natural motion of the knee joint as well as providing the desired support for relieving pain and as a walking aid etc. However, because of the lateral end medial hinge mechanisms, it is impossible to adjust such orthotic devices in a frontal plane into varus or valgus.
Another type of orthotic devices is the one-sided knee joint, that is having a hinge mechanism on one side only, an example of which may be seen from U.S. Pat. No. 5,277,698. In this knee brace a sagittal adjustment is possible through use of the hinge elements comprising circular hinge elements. The knee brace is capable of applying a force to the knee by means of a cross-strap tightenable across the knee. The knee brace also includes a multiaxial hinge mechanism.
Another example of the one-sided knee joint may be seen from U.S. Pat. No. 5,458,565. In this knee brace a restoring force is achieved through use of a rotary hinge assembly together with an inflatable and deflatable fluid-containing pad positioned between the hinge assembly and the knee joint. The restoring force is adjustable by selective inflation and deflation of the pad. The knee brace also includes a multiaxial geared hinge mechanism.
A problem with this type of knee brace is that the multiaxial hinge mechanism does not provide the best possible natural movement of the knee joint. Also, the cross-strap as well as the fluid-containing pad are bulky and difficult to adjust to an accurate correction force.
The present invention uses another approach to providing the correction force, thus avoiding the above-mentioned problems. In the present invention, the hinge mechanism is adjustable to provide the correction force on the thigh and shin cuffs. Also, the knee brace comprises a four-axes joint providing a more natural movement simulating the movement of the knee.
The present invention provides a knee brace with sagittal adjustment comprising a thigh cuff and a shin cuff interconnected by a hinge portion on one side of the knee brace only.
According to the invention, the hinge portion is capable of providing a sagittal correction force to correct the position of a knee joint into varus or valgus. Preferably, the hinge portion comprises a tilting mechanism which may be locked in an angled state to provide the sagittal correction force.
The invention is defined in the accompanying claim 1 while preferred embodiments are set forth in the dependent claims.